Characterisation of dihydrodipicolinate synthase (DHDPS) from Bacillus anthracis.

Bacillus anthracis is a Gram-positive spore-forming bacterium that is the causative agent of anthrax disease. The use of anthrax as a bioweapon has increased pressure for the development of an effective treatment. Dihydrodipicolinate synthase (DHDPS) catalyses the first committed step in the biosynthetic pathway yielding two essential bacterial metabolites, meso-diaminopimelate (DAP) and (S)-lysine. DHDPS is therefore a potential antibiotic target, as microbes require either lysine or DAP as a component of the cell wall. This paper is the first biochemical description of DHDPS from B. anthracis. Enzyme kinetic analyses, isothermal titration calorimetry (ITC), mass spectrometry and differential scanning fluorimetry (DSF) were used to characterise B. anthracis DHDPS and compare it with the well characterised Escherichia coli enzyme. B. anthracis DHDPS exhibited different kinetic behaviour compared with E. coli DHDPS, in particular, substrate inhibition by (S)-aspartate semi-aldehyde was observed for the B. anthracis enzyme (K(si(ASA))=5.4+/-0.5 mM), but not for the E. coli enzyme. As predicted from a comparison of the X-ray crystal structures, the B. anthracis enzyme was not inhibited by lysine. The B. anthracis enzyme was thermally stabilised by the first substrate, pyruvate, to a greater extent than its E. coli counterpart, but has a weaker affinity for pyruvate based on enzyme kinetics and ITC studies. This characterisation will provide useful information for the design of inhibitors as new antibiotics targeting B. anthracis.

Inhibiting protein-protein interactions as an emerging paradigm for drug discovery.

Association of proteins into homo- and hetero-oligomers plays an important role in a plethora of biological phenomena. Inhibition of these interactions is increasingly recognized as a valuable new direction in drug design. In this mini-review we consider inhibition of protein misfolding and aggregation, molecules that disrupt enzyme quaternary structure, and signaling inhibitors, as emerging drugs.

Synthesis of beta-hydroxy-beta-(fluoronitrophenyl)alanines: vital components in the assembly of biologically active cyclic peptides.

[formula: see text] Numerous biologically active cyclic peptides, such as the antibiotic vancomycin, contain amino acid residues connected through side-chain biaryl or aryl-alkyl ether linkages. Nucleophilic aromatic substitution reactions have recently been shown to provide a general method for the formation of such ether linkages, and consequently the synthesis of functionalized fluoronitro-substituted aromatic amino acids is of great interest. Herein, a method for the stereospecific synthesis of 3-fluoro-4-nitro- and 4-fluoro-3-nitro-threo-beta-hydroxyphenylalanine is described.

Total synthesis of (-)-reveromycin B.

[structure: see text] The total synthesis of the epidermal growth factor inhibitor reveromycin B (2) is described. A novel, convergent, and stereoselective reaction sequence was utilized to construct the 5,6-spiroketal system 10 which was converted into the natural product 2 by a 16-step sequence.

Preparation of beta-nitroalanine using the Easton three-component coupling method.

A simple one-step preparation of beta-nitroalanine has been developed using the Easton three-component coupling method. To date one limitation of this method has been that use of nitromethane as the nitroalkane component does not yield beta-nitroalanine. We report that use of the dipotassium salt of nitroacetic acid in the Easton three-component coupling gives beta-nitroalanine in high yield, presumably via facile decarboxylation of a beta-nitroaspartate intermediate.

Total synthesis of the epidermal growth factor inhibitor (-)-reveromycin B.

The total synthesis of the epidermal growth factor inhibitor reveromycin B (2) in 25 linear steps from chiral methylene pyran 13 is described. The key steps involved an inverse electron demand hetero-Diels-Alder reaction between dienophile 13 and diene 12 to construct the 6,6-spiroketal 11 which upon oxidation with dimethyldioxirane and acid catalyzed rearrangement gave the 5,6-spiroketal aldehyde 9. Lithium acetylide addition followed by oxidation/reduction and protective group manipulation provided the reveromycin B spiroketal core 8 which was converted into the reveromycin A (1) derivative 6 in order to confirm the stereochemistry of the spiroketal segment. Introduction of the C1-C10 side chain began with sequential Wittig reactions to form the C8-C9 and C7-C6 bonds, and a tin mediated asymmetric aldol reaction installed the C4 and C5 stereocenters. The final key steps to the target molecule 2 involved a Stille coupling to introduce the C21-C22 bond, succinoylation, selective deprotection, oxidation, and Wittig condensation to form the final C2-C3 bond. Deprotection was effected by TBAF in DMF to afford reveromycin B (2) in 72% yield.